Field of the Invention
The invention relates to field of display technology, and particularly to a display substrate and a method of manufacturing the same, a display device.
Description of the Related Art
Traditional processes of manufacturing a liquid crystal panel generally comprise forming an array of thin film transistors on an array substrate (TFT) and forming a black matrix and a color filter layer on a color filter substrate and then assembling them to form a cell and finally packaging the cell. The black matrix is provided for separating the adjacent portions of the color filter layer to form sub-pixels, preventing color mixture or light leak. If the cell assembling process is not accurate such that the thin film transistor is not aligned with the color filter layer, several undesirable effects will be caused.
With the development of the liquid crystal display industry, a Color filter On Array (COA) technology gradually has become mature, in which technology the black matrix and the color filter layer which are conventionally formed on the color filter substrate are transferred to the array substrate, thus the problem arising from poor accuracy of the cell assembling process can be fundamentally solved, and there are further advantageous effects including improvement of aperture ratio and quality of the display panel, etc.
However, it is difficult to identify the position aligning marks during exposing, if the black matrix is formed on the array substrate rather than on the color filter substrate, because the black matrix is made of a material with high optical density and is hard to be identified. In this instance, it is hard to align a mask during exposure. If the black matrix is made of a material with a low optical density, the light shielding effect is degraded although the discrimination of the position aligning marks may be improved. FIG. 1A is a schematic plan view of a display substrate coated with a film 50 of a black matrix and FIG. 1B is a cross section view of a position aligning region in a square shape shown in FIG. 1A, taken along line A-A. From FIGS. 1A and 1B, it can be seen that the film 50 of the black matrix completely covers the position aligning marks 2 after coated on the array substrate. As the film 50 has a typical thickness of 1 μm, the level drop or height difference between the position aligning marks 2 that have been covered by the film 50 of the black matrix and the layers therearound is reduced, such that the position aligning marks are hard to be identified using a surface profile detecting method.
It is needed to provide a display substrate in COA structure that may solve the problem in prior art and achieves convenient and accurate position alignment.